Eye drops for medical use must be applied in a controlled, fixed quantity.
An ordinary eye drop container in wide use, which can control the quantity of application, has an injection molded inner nozzle tip fitted in and fixed to a tubular portion of a molded container body. This nozzle tip defines a hollow in the form of a bottomed cone having an inside diameter increasing toward a tip end thereof, and a small diameter instilling hole extending through a central position of the bottom of the hollow for controlling the quantity of the ophthalmic solution pushed out of the container body. An injection molded cap, having a stopper-like projection for fitting in and sealing the hollow in the form of a bottomed cone, is meshed with and mounted on a male screw formed on an outer peripheral surface of the tubular portion of the container body.
This eye drop container, with the hollow in the form of a bottomed cone and the small diameter instilling hole extending through the central position of the bottom of the hollow, can reliably instill the solution constantly in a fixed quantity as the container body is pressed. However, dies are required to injection mold the three components separately from one another, and each component requires a cleaning and sterilizing operation, which results in increased manufacturing costs.
On the other hand, unitary molded containers are used which achieve reduced manufacturing costs and yet can retain the function of an eye drop container. Such a container has a container body formed of a thermoplastic material (popularly called a bottle pack type container in which a solution is filled and sealed at the time of blow molding or vacuum molding. A cap, having a needle-like projection formed integral therewith for penetrating and forming a instillation channel in the tip portion of the container body, is detachably meshed with a male screw formed on an outer peripheral surface on the tip portion of the container body. The cap is meshed further downward than the usual stopping position, whereby the needle-like projection of the cap penetrates and forms an instillation channel in the tip portion of the container body.
The above eye drop container of the bottle pack type has the advantage of reduced manufacturing costs over the eye drop container using the inner nozzle tip formed by injection molding. However, since the instillation channel is formed by the needle-like projection of the cap breaking through the tip end of the container body, the cap must be properly screwed to a further tightened position from the usual stopping position. Otherwise, the shape and size of the instillation channel may lack uniformity, resulting in variations in the quantity of ophthalmic solution pushed out of the container body.
When the cap is tightened excessively from the usual stopping position after the tip end of the container body is penetrated to form a instillation channel therein, the instillation channel is enlarged by the needle-like projection of the cap with each excessive tightening turn. Thus, the quantity of the solution to be pushed out of the container body may gradually increase.
It is therefore necessary to provide sufficient information as to the proper use of the eye drop container. However, even with sufficient information given, it has been difficult to avoid the above misuse because users are inclined to mesh the cap without enough caution for penetrating the instillation channel or tighten the cap excessively.